This invention relates to a power saving apparatus for an electronic musical instrument for digitally producing musical tones.
Recently, electronic musical instruments have become very popular. In particular, compact electronic musical instruments which use LSIs (large scale integrated circuits) for tone generating circuits and are powered by batteries, have been developed.
In the usual battery-powered electronic musical instrument, power is inefficiently consumed if a power switch of the instrument is held "on". If the instrument is left with the power switch held "on", the battery is soon used up, and the battery must be replaced frequently. This is not only inconvenient but is also uneconomical. Such inefficient power consumption is also the case with an electronic musical instrument which is powered by a commercial power source.
Accordingly, there has been developed an electronic musical instrument, in which the power source is turned "off" automatically when the power source switch has been held "on" without the instrument being played for a predetermined period of time. For example, this is disclosed in Japanese patent disclosure (KOKAI) No. 56-40895 or in a U.S. patent application Ser. No. 185,411 filed Sept. 9, 1980, assigned to the assignee of the present invention and now abandoned. In this case, however, if the predetermined period of time is too short, the player must always bear in mind whether power is being supplied while playing. On the other hand, if the predetermined period of time is too long, a considerable amount of power is wasted if the instrument is left with the power switch held "on". In either case, the power source is held "on" until the predetermined period of time has elapsed, and power consumed during this period is often wasted.